Search

The La0.5Sr0.5Fe0.9Mo0.1O3 − δ-x wt.% SDC (LSFMo-xSDC, x = 0, 20, and 30) samples were evaluated as potential cathodes for solid oxide fuel cells (SOFCs) based on both La0.9Sr0.1Ga0.8Mg0.2O3 − δ (LSGM) and Sm0.2Ce0.8O2 − δ (SDC) electrolytes. The LSFMo cathode is chemically compatible with the LSGM and SDC electrolytes with temperature up to 1000 °C. Through the comparison of the polarization resistances (Rp) of the LSFMo cathode on LSGM and SDC electrolytes, only a small difference of ~ 13-15% in the Rp was obtained. To further improve the electrochemical performance of the LSFMo cathode, 20 and 30 wt.% SDC were introduced into the LSFMo cathode. The LSGM/SDC-supported single cell with LSFMo-20SDC composite cathode was found to show the optimal performance and excellent power cycle and long-time stability. In addition, the electrical conductivity and thermal expansion coefficient (TEC) for the LSFMo-20SDC cathode were also detected and evaluated. Our results show that the LSFMo-20SDC is a very promising candidate for use in the cathode of SOFC. [ABSTRACT FROM AUTHOR]

The 0.1 mol% Er3+ and 0-2 mol% Yb3+ codoped Al2O3 powders were prepared by the sol-gel method, and the phase structure, including only two crystalline types of doped Al2O3 phase, γ-(Al,Er,Yb)2O3 and θ-(Al,Er,Yb)2O3, was detected at the sintering temperature of 100°C. The visible and near infrared emissions properties depended strongly on the Yb3+ codoping, and the corresponding maximal peak intensities centered at about 523, 545, 660 and 1533 nm were obtained respectively for the 0.1 mol% Er3+ and 0.5 mol% Yb3+ codoped Al2O3 powders, which were composed of θ-(Al,Er,Yb)2O3 and a small amount of γ-(Al,Er,Yb)2O3 phases. The two-photon absorption process was responsible for the visible up-conversion emissions, and the one-photon absorption process was involved in the near infrared emissions of the Er3+-Yb3+ codoped Al2O3 powders. [ABSTRACT FROM AUTHOR]

Perovskite oxides La x Sr 1–x Co 0.9 Sb 0.1 O 3– δ (LSCSbx, x=0.0–0.8) are investigated as IT–SOFC cathodes supported with La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3– δ (LSGM) electrolyte. All LSCSbx oxides have a tetragonal distorted perovskite structure with s.g. P4/mmm , while a La 2 Co 2 O 5 impurity phase was observed within La doping levels at x=0.6–0.8. The LSCSb0.4 has a good chemical compatibility with LSGM electrolyte for temperatures up to 1050 °C. XPS examinations indicate the existence of Co 3+ /Co 4+ mixed valence states in LSCSbx. The conductivity increases with La doping and the LSCSbx with x=0.4 exhibits the highest electrical conductivity (e.g., 673–1637 S cm −1 at 300–850 °C). The thermal expansion coefficient (TEC) decreases from 25.89×10 –6 K –1 for x=0.0 to 18.5×10 –6 K –1 for x=0.6 at 30–900 °C. Among the LSCSbx compositions, the LSCSb0.2 exhibits the lowest polarization resistance ( R p ), which is merely 0.069 Ω cm 2 at 700 °C. The maximum power density of the cell with LSCSb0.2 cathode on 300 µm thick LSGM electrolyte attains 564 mW cm –2 at 850 °C, which is higher than that of SrCo 0.9 Sb 0.1 O 3– δ (SCSb) cathode. All of the results indicate that LSCSb0.2 is a promising material for application in IT–SOFCs cathodes. [ABSTRACT FROM AUTHOR]

Ba x Sr 1− x Co 0.9 Sb 0.1 O 3− δ (BSCSbx, x = 0.0–0.8) are investigated as cathodes for intermediate temperature solid oxide fuel cells (IT-SOFCs). BSCSbx oxides are crystallized in a tetragonal structure with s.g. P4/mmm . XPS analysis shows that Ba doping reduces valence state of Co ions: Co in SrCo 0.9 Sb 0.1 O 3− δ is prone to Co 4+ , while Co in Ba doped SrCo 0.9 Sb 0.1 O 3− δ becomes more prone to Co 3+ . Oxygen deficiency δ increases with Ba doping even at high temperatures. Conductivity is found to decrease with Ba doping. Thermal expansion coefficient (TEC) decreases from 20.6 × 10 −6 K −1 for x = 0.0 to 18.4 × 10 −6 K −1 for x = 0.6 at 30–1000 °C. With increasing x from 0.0 to 0.6, polarization resistance ( R p ) decreases monotonously, and then increases with further increasing x. The lowest R p of 0.081 Ω cm 2 at 700 °C is obtained for BSCSb0.6 cathode. At 700–850 °C, the R p of BSCSb0.6 is mainly contributed from electron charge transfer; however, below 700 °C, ion charge transfer plays a more important role in R p . Maximum power densities of the cell with BSCSb0.6 cathode on 300-μm thick La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3− δ (LSGM) electrolyte attain 306–944 mW cm −2 at 700–850 °C. These results indicate that BSCSb0.6 is a promising cathode for application in IT-SOFC. [ABSTRACT FROM AUTHOR]

Ba0.6Sr0.4Co0.9Nb0.1O3−δ (BSCN)–xGd0.1Ce0.9O1.95 (GDC) composites with various GDC contents (x = 0–40, wt%) have been investigated for their potential application in IT-SOFCs. The effects of GDC addition on thermal expansion and electrochemical performances were studied. Thermal expansion measurement indicates that thermal expansion coefficients (TECs) decrease with increasing GDC content; in addition, GDC plays a catalytic role during the process of low-temperature thermal-driven reduction of Co4+ to Co3+. Polarization resistance (R p) measurement indicates that the proper addition of GDC improves electrochemical performance of BSCN cathode. The optimum GDC addition to BSCN cathode is 20 wt% with the lowest R p of 0.042 Ω cm2 at 700 °C. The maximum power density of a cell with BSCN–20GDC cathode on 300 μm-thick GDC electrolyte achieves 460–880 mW cm−2 at 700–800 °C. The excellent electrochemical performance of BSCN–20GDC composite cathode is ascribed to its much finer microstructure and larger cathode/electrolyte/gas triple phase boundary (TPB) areas. [ABSTRACT FROM AUTHOR]